A Kaplan turbine is a device for extracting kinetic energy from a flowing stream of water and converting same into electric power. In such a device a driven member (e.g. a set of turbine blades) is arranged in the flowing stream. Some of the kinetic energy in this stream is converted into rotation of the driven member, which, in turn, causes rotation of a turbine shaft. This rotational energy is then transferred via a suitable transmission to the drive shaft of a generator, thereby generating electricity.
In order to obtain a higher yield from water power, Kaplan turbines have become of increasingly larger construction. In this way, the forces acting on the individual parts have also increased. Thus, Kaplan turbines can achieve outputs of more than 3000 kW, in which case the turbine blades may have a diameter of more than 3 meters.
Tensile and compressive forces, as well as bending moments, can be introduced by the turbine blades into the turbine shaft. These forces and moments are taken up by thrust and radial bearings and introduced into the foundation via the housing.
A poster of Voest-Alpine (PITTYPE TURBINE), describes a Kaplan turbine in which the turbine blades, turbine shaft, gear assembly (transmission), drive shaft and generator are arranged in a line. The tensile and compressive forces introduced by the turbine blades are taken up by a pressure collar which is arranged on the turbine shaft. The turbine shaft is mounted on a radial bearing so that the gear assembly which is arranged in line with the turbine shaft requires at least one additional radial bearing.
Difficulties in manufacture are encountered in connection with the pressure collar upon the machining of the pressure-bearing surfaces, particularly in connection with the final shaping since it is not possible, for instance, to grind this in one chucking. These difficulties which occur upon new manufacture are even greater in the case of possible repair work on an installed turbine.
The housing which is to be brought into the water flowing around it has a large volume in radial and axial directions since it must completely surround parts which are arranged in a line.
It is, therefore, an object of the invention to create a Kaplan turbine which poses the least possible resistance to the flow of water and assures, by means of a smaller number of bearing elements which can be easily machined from a manufacturing standpoint, a dependable fastening of the turbine shaft and the gear assembly.